Various electronic calipers are known that use electronic position encoders. These encoders are generally based on low-power inductive, capacitive, or magnetic position sensing technology. In general, an encoder may comprise a readhead and a scale. The readhead may generally comprise a readhead sensor and readhead electronics. The readhead outputs signals that vary as a function of the position of the readhead sensor relative to the scale, along a measuring axis. In an electronic caliper, the scale is generally affixed to an elongated scale member that includes a first measuring jaw and the readhead is affixed to a slider which is movable along the scale member and which includes a second measuring jaw. Thus, measurements of the distance between the two measuring jaws may be determined based on the signals from the readhead.
Exemplary electronic calipers are disclosed in commonly assigned U.S. Pat. No. RE37490, U.S. Pat. Nos. 5,574,381, and 5,973,494, each of which is hereby incorporated by reference in its entirety. Caliper technology emphasizes the need for lower power consumption, for example, U.S. Pat. No. 5,973,494 discloses configurations which reduce power consumption in a caliper. Nonetheless, even in low power configurations, batteries need replacement periodically. This is seen by some users as an unwanted inconvenience and/or expense. A caliper which eliminates battery replacement, or significantly postpones replacement, is desirable.